Responsible for the degradation of damaged proteins, Proteasomes complete the process of proteolysis. This chemical reaction breaks down peptide bonds. The enzymes that are responsible for this type of reaction are commonly referred to as proteases.
Proteasome Mechanism and Function
The proteasomes are a part of the mechanism by which cells regulate the particular levels of proteins and continue to degrade proteins that have been misfolded. The cells that need to be degraded are typically tagged with a much smaller protein which will typically be known as ubiquitin. The reaction that occurs here is known as ubiquitin ligases.
After a protein has been tagged with a particular ubiquitin molecule, a signal is created. It causes various other ligases to attach to additional ubiquitin molecules as well. The result of this creates the polyubiquitin chain. This is bound by the proteasome which is then encouraged to further degrade and eliminate the protein that has been tagged.
The mechanism here will cause peptides to be yielded and these are between seven or eight amino acids in length. These can lead to the synthesizing of brand new proteins as well. These will typically be created in the cytoplasm.
These processes will typically occur through cellular stress. Potential causes include heat shock, infection and oxidative damage to name just a few possibilities. During this time certain proteins are targeted for degradation and this is expressed through effective tagging. Various proteins have also been seen to cause an increase in activity through the ubiquitin-proteasome system. It is important to realize that these proteins including Hsps27 are not actually direct participants in the process though they certainly seem to play a role.
There are also mechanisms that exist which are used to further promote the degradation of cells that have been damaged through oxidation. This occurs through the proteasome system as well.
It’s true to say that proteasome is responsible for a wide range of different interactions in the body and specific cellular processes This includes the regulations of the gene expression, the cell cycle and the response to any oxidative stress.
The proteasome has a cylindrical structure. This contains a unique core of four rings that are stacked together. This forms the central core. These are formed of several individual proteins. They are also made of seven different subunits that contain three to seven different proteins that are entirely individual. There are also various active sites which are located on the interior surface of the different rings.
This means that the target protein must enter the central pore before it is effectively degraded through the process. At the same time, the two outer rings will contain seven different subunits. The function of these is to effectively maintain the gate by which protein enters through.
These subunits function through the control of being bound to a ‘cap’ structure. These are also known as regulatory particles which are a key part of the degradation process.